tail script

leostereo has asked for the wisdom of the Perl Monks concerning the following question:

hi guys, I would like ask why my script is not working as expected, everthing is working good excep the line that exec system ......, it is strange but if I exec the line on a separate script it works and do the job, any help would be preciated.. following , the code

#!/usr/bin/perl -w
use strict;
use File::Tail;

my $file = File::Tail->new(
        name =>'/var/log/dhcpd.log', 
        interval => 1, 
        maxinterval => 1, 
        resetafter=> 5, 
        );





  while (defined(my $line=$file->read)) {
         print $line,"\n"; 
                if ($line =~ /^(.*) mdz-shaper1 dhcpd: DHCPACK on ([0-
+9\.]+) to ([[:xdigit:]:]+).* ([0-9\.]+)/) {
                        my ($date,$client_ip,$client_mac,$master_ip) =
+ ($1,$2,$3,$4);


                system "sed -i '/$client_mac/d' /opt/btb_webservice/ve
+r3/lease_list.txt";
                if(($client_ip)&&($client_mac)&&($master_ip)){
              system 'echo "'.$date.' '. $client_ip.' '.$client_mac.' 
+'. $master_ip.'"'.' >> /opt/btb_webservice/ver3/lease_list.txt';
                }
        }

}
1;
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Re: tail script by NetWallah (Canon) on Dec 09, 2015 at 23:11 UTC
Is the file "/opt/btb_webservice/ver3/lease_list.txt" writable ? Mixing shell and perl without error checking is error prone. I'd recommend using the perl module File::Inplace to replace your "sed" call, using something like (untested): `use File::Inplace; my $editor = File::Inplace::->new( file => "/opt/btb_webservice/ver3/lease_list.txt"); while (my ($line) = $editor->next_line) { $line =~/$client_mac/ or next; $editor->replace_line(""); # Zap line } $editor->commit;` [download] Our business is run on trust. We trust you will pay in advance.	[reply] [d/l]
Re: tail script by jcb (Parson) on Dec 09, 2015 at 22:52 UTC
Your code uses `system` twice, which one is not working? While `sed` is complex enough that writing that out in Perl may be more work than it is worth, you should consider the two-argument form of system when calling it. The use of `system` merely to append a line to a file sticks out, however. I suggest using open instead: `open LIST, '>>', '/opt/btb_webservice/ver3/lease_list.txt' or die "/op +t/btb_webservice/ver3/lease_list.txt: $!"; print LIST join(' ',$date,$client_ip,$client_mac,$master_ip),"\n" or d +ie "/opt/btb_webservice/ver3/lease_list.txt: $!"; close LIST or die "/opt/btb_webservice/ver3/lease_list.txt: $!";` [download]	[reply] [d/l] [select]